Abstract: | Lippia alba is empirically used for infusions, teas, macerates, and
hydroalcoholic extracts because of its antispasmodic, analgesic, sedative, and
anxiolytic effects. Citral is a mixture of trans-geranial and cis-neral and is the
main constituent of L. alba essential oil and possesses analgesic,
anxiolytic, anticonvulsant, and sedative effects. The present study evaluated the
effects of the essential oil of L. alba (EOLa) and citral on
compound action potentials (CAPs) in Wistar rat sciatic nerves. Both drugs inhibited
CAP in a concentration-dependent manner. The calculated half-maximal inhibitory
concentrations (IC50) of peak-to-peak amplitude were 53.2 µg/mL and 35.00
µg/mL (or 230 µM) for EOLa and citral, respectively. Peak-to-peak amplitude of the
CAP was significantly reduced by 30 µg/mL EOLa and 10 µg/mL citral. EOLa and citral
(at 60 and 30 µg/mL, values close to their respective IC50 for CAP
blockade) significantly increased chronaxy and rheobase. The conduction velocity of
the first and second CAP components was statistically reduced to ∼86% of control with
10 µg/mL EOLa and ∼90% of control with 3 µg/mL citral. This study showed that EOLa
inhibited nerve excitability and this effect can be explained by the presence of
citral in its composition. Both EOLa and citral showed inhibitory actions at lower
concentrations compared with other essential oils and constituents with local
anesthetic activity. In conclusion, these data demonstrate that EOLa and citral are
promising agents in the development of new drugs with local anesthetic activity. |